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david yost 27th October 2008 07:49 PM

Any experience here with thin wool felt?
I am trying to come up with a mechanical method to increase the mid-high freq. dispersion of the classic Acoustat 8-9" panels. My first thought is to mask the panels with layers of felt cloth starting about 1/2" from the vertical centerline to the outside edges of the panels. The next layer maybe 1" from the centerline to the edges, etc., all the way to the edges--maybe 5-6 layers in all. The goal is to progressively "widen" the apparent source as frequency goes down. I guess that trial and error with measurements would probably be the best way to do this...but any and all thoughts/suggestions are welcome.


moray james 29th October 2008 08:37 PM

physical damping to shade response of the panel
Did exactly that to a couple of sets of Acoustat's in the early 90's it works and worked well, better I thought than the Spectra approach tho that is supposed to make the load on your amp easier. I removed the felt strips of the back of the panels and treated the back side of the panel the same as the front. I left a vertical strip one inch wide open with no damping then damped the next one inch on either side with a layer of damping abd then used two layers of dqmping to do the remainder of the panel on either side. So three sections zero then light then heavier. Like i said it worked very well. I used a very light misting of 3M 77 to stick the felt down. Both pair are still in service today. On a panel this narrow I really don't see any benefit of more than three sections and if I recall it worked out being symetrical about the two central vertical rows of louvre.

david yost 29th October 2008 09:18 PM

Hi, Moray

That is very encouraging news! You have already done exactly what I would like to do.

At AudioAsylum I recently asked about the prospect of using the center 2 vertical panels of my 6's full range with the outer 4 panels driven by the low frequency transformers only. Have you ever tried this? If it works, I may try the felt masking trick too.

My goal is to get the imaging of the 1+1's (or better) with the bass power of the 6's--best of all worlds.

moray james 29th October 2008 09:30 PM

sort of....
Why not run the two inside vertical panels off of the mid/treble transformer and the remaining four panels off of the bass transformer? That way you can direct yhr inside two panels at your listening location and the other four panels will be angled away from you. That ought to get you close to a 0ne plus 0ne set up but with bass. I would suggest that you felt damp the entire surface (front and back) of the four bass panels as you want to damp out as much mid frequency as possible from those panels. The bass will just fire straight through the damping. You will also gain far better air load on those diaphragms. I did not use felt but non woven polyester material and layered u with the lightest possible misting of spray adhesive so I would not clog the material. The material was sewing interface material from a fabric shop and it does come in different weights. A good thick heavy weighr would eliminate the need for glueing up any layers. Hope this helps.

moray james 29th October 2008 10:50 PM

foof for thought...
David there is also no reason why you cannot use a combination of an RC delay as used in the Spectra series (Acoustat) in combination with fabric damping together. Further you can play with the polar response of the speaker a little by damping the whole back section of the main panels while you three layer damp the front side. This will yield a slight cardioide polar pattern which will make speaker placement a little easier. There is lots to read on RC delays over at the Dutch ESL site in case you have not seen it here is a link.

david yost 29th October 2008 11:25 PM

Thanks for the links, Moray. Unfortunately, I am poor with Dutch, but I get the drift...very nice DIY site with very creative people.

moray james 29th October 2008 11:33 PM

google or Bable will give you a fairly good text to read in english. Drawings and pictures show you all the rest.

bear 30th October 2008 05:53 PM


I'd think the "plastic louvres" are a serious issue WRT HF dispersion with the Acoustats...

If you play them outdoors, as I have, one might be amazed at exactly how beamy they actually are. One doesn't get the same sense of the narrowness in a room environment at all...


PS. still wrapping sandwiches! ;)

PPS. can you post the link to the RC delays on the Dutch site? I didn't see it in a quick Google'd look... tnx.

moray james 30th October 2008 11:39 PM

look in the projects...

moray james 31st October 2008 06:03 AM

Bear it depends...
depends on how you look at it you said

"Quote I'd think the "plastic louvres" are a serious issue WRT HF dispersion with the Acoustats...

If you play them outdoors, as I have, one might be amazed at exactly how beamy they actually are. One doesn't get the same sense of the narrowness in a room environment at all..."

If you are looking to have wide dispersion speakers yes the cubes are an issue. If you are looking for a directional speaker then they are a bonus. My good buddy Ger has some 0ne plus 0nes and when driven on any one of several good amps that he has they do not exhibit the head in the vice that I first noticed when I listened to them several decades ago on ams such as the HAFLER. Not saying they are not directional but the difference between a good amp that will handle the load and one that onlt tolerates the load is substantial. Me I am a directional kind of guy so you know my bias. Amps that run well but only put up with the load just do not show what these speakers can do. As always I recommend that owners get their diaphragm charge up to 5 Kv the difference is amazing. Only costs a few bucks. Do it do it now. Over and out.

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